Introduce an Attribute object to handle the type casting dance

There's a lot more that can be moved to these, but this felt like a good
place to introduce the object. Plans are:

- Remove all knowledge of type casting from the columns, beyond a
  reference to the cast_type
- Move type_cast_for_database to these objects
- Potentially make them mutable, introduce a state machine, and have
  dirty checking handled here as well
- Move `attribute`, `decorate_attribute`, and anything else that
  modifies types to mess with this object, not the columns hash
- Introduce a collection object to manage these, reduce allocations, and
  not require serializing the types

1 files changed, 8 insertions, 12 deletions

diff --git a/activerecord/lib/active_record/attribute_methods.rb b/activerecord/lib/active_record/attribute_methods.rb
index e626227e7e..ddccb29d09 100644
--- a/activerecord/lib/active_record/attribute_methods.rb
+++ b/activerecord/lib/active_record/attribute_methods.rb
@@ -261,9 +261,9 @@ module ActiveRecord
 
       # If the result is true then check for the select case.
       # For queries selecting a subset of columns, return false for unselected columns.
-      # We check defined?(@raw_attributes) not to issue warnings if called on objects that
+      # We check defined?(@attributes) not to issue warnings if called on objects that
       # have been allocated but not yet initialized.
-      if defined?(@raw_attributes) && @raw_attributes.any? && self.class.column_names.include?(name)
+      if defined?(@attributes) && @attributes.any? && self.class.column_names.include?(name)
         return has_attribute?(name)
       end
 
@@ -280,7 +280,7 @@ module ActiveRecord
     #   person.has_attribute?('age')    # => true
     #   person.has_attribute?(:nothing) # => false
     def has_attribute?(attr_name)
-      @raw_attributes.has_key?(attr_name.to_s)
+      @attributes.has_key?(attr_name.to_s)
     end
 
     # Returns an array of names for the attributes available on this object.
@@ -292,7 +292,7 @@ module ActiveRecord
     #   person.attribute_names
     #   # => ["id", "created_at", "updated_at", "name", "age"]
     def attribute_names
-      @raw_attributes.keys
+      @attributes.keys
     end
 
     # Returns a hash of all the attributes with their names as keys and the values of the attributes as values.
@@ -400,11 +400,10 @@ module ActiveRecord
 
     protected
 
-    def clone_attributes(reader_method = :read_attribute, attributes = {}) # :nodoc:
-      attribute_names.each do |name|
-        attributes[name] = clone_attribute_value(reader_method, name)
+    def clone_attributes # :nodoc:
+      @attributes.each_with_object({}) do |(name, attr), h|
+        h[name] = attr.dup
       end
-      attributes
     end
 
     def clone_attribute_value(reader_method, attribute_name) # :nodoc:
@@ -424,7 +423,7 @@ module ActiveRecord
 
     def attribute_method?(attr_name) # :nodoc:
       # We check defined? because Syck calls respond_to? before actually calling initialize.
-      defined?(@raw_attributes) && @raw_attributes.include?(attr_name)
+      defined?(@attributes) && @attributes.include?(attr_name)
     end
 
     private
@@ -465,9 +464,6 @@ module ActiveRecord
     end
 
     def typecasted_attribute_value(name)
-      # FIXME: we need @attributes to be used consistently.
-      # If the values stored in @attributes were already typecasted, this code
-      # could be simplified
       read_attribute(name)
     end
   end